The invention is generally related to the field of forming MOSFET transistors and more specifically to a method of forming an ultra-thin gate oxide.
Presently, there is a great demand for shrinking semiconductor devices to provide an increased density of devices on the semiconductor chip that are faster and consume less power. The scaling of devices in the lateral dimension requires vertical scaling as well so as to achieve adequate device performance. This vertical scaling requires the effective electrical thickness of the gate dielectric to be reduced so as to provide the required device performance.
Silicon dioxide has been the preferred gate dielectric material. Traditional methods of reducing the silicon dioxide thickness involve one or more of the following: reduce the oxidation temperature; change the oxidation gas; or dilute the oxidation gas. Reducing the oxidation temperature has the disadvantage of degrading the GOI (gate-oxide integrity). Due to GOI problems and safety (some oxidizing agents being more explosive, reactive, toxic than others), the newer technologies are quickly reaching the limits of the traditional process by requiring effective thicknesses of the silicon dioxide below 20 Angstroms.
One prior art method investigated silicon dioxide deposited using chemical vapor deposition (CVD). SiH4, CO2, and H2 were combined to form a silicon dioxide layer suitable for use in field oxidation. Combining SiH4, CO2, and H2 allowed silicon dioxide to be formed without consuming the underlying silicon. In one experiment, 1.2% CO2 in 110 liters/min H2 at 1000xc2x0 C. for 1 hr produced 15 xc3x85 of SiO2 and 1.2% N2O in 110 liters/min, H2 at 1000xc2x0 C. for 1 hr produced 600 xc3x85 of SiO2.
A method of forming an ultra-thin gate oxide for a field effect transistor is disclosed herein. The gate oxide is formed by combining an oxidizing agent with an etching agent and adjusting the partial pressures to controllably grow a thin high quality oxide.
An advantage of the invention is providing a thin ( less than 20 Angstroms) high-quality gate oxide.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.